One of the main goals of computer graphics is the fast synthesis of photorealistic image of virtual 3D scenes. The work presented in this thesis addresses this goal of speed and realism. In real-time realistic rendering, we encounter certain problems that are difficult to solve in the traditional 3-dimensional geometric space. We show that using an image-space approach can provide effective solutions to these problems. Unlike geometric space algorithms that operate on 3D primitives such as points, edges, and polygons, image-space algorithms operate on 2D snapshot images of the 3D geometric data. Operating in image-space effectively decouples the geometric complexity of the 3D data from the run-time of the rendering algorithm. Other important advantages of image-space algorithms include ease of implementation on modern graphics hardware, and fast computation of approximate solutions to certain lighting calculations. We have applied the image-space approach and developed algorithms for three prominent problems in real-time realistic rendering, namely, representing and lighting large 3D scenes in the context of grass rendering, rendering caustics, which is a complex indirect illumination effect, and subsurface scattering for rendering of translucent objects.

As the quest for more realistic computer graphics marches steadily on, the demand for rich and detailed imagery is greater than ever. However, the current "sweet spot" in terms of price, power consumption, and performance is in commodity hardware. If we desire to render scenes with tens or hundreds of millions of polygons as cheaply as possible, we need a way of doing so that maximizes the use of the commodity hardware we already have at our disposal. Techniques such as normal mapping and level of detail have attempted to address the problem by reducing the amount of geometry in a scene. This is problematic for applications that desire or demand access to the scene's full geometric complexity at render time. More recently, out-of-core techniques have provided methods for rendering large scenes when the working set is larger than the available system memory. We propose a distributed rendering architecture based on message-passing that is designed to partition scene geometry across a cluster of commodity machines in a spatially coherent way, allowing the entire scene to remain in-core and enabling the construction of hierarchical spatial acceleration structures in parallel. The results of our implementation show roughly an order of magnitude speedup in rendering time compared to the traditional approach, while keeping memory overhead for message queuing around 1%.

The growing demand for realistic renderings in both film and games has led to a number of proposed solutions to the Global Illumination problem. In order to imitate natural lighting, it is necessary to gather indirect illumination of the surrounding environment for lighting computations. This is a computationally expensive problem, requiring the sampling or rasterization of the hemisphere surrounding each ray intersection, to which there is no standardized solution. In this thesis we propose a new method of approximation using environment maps for caching radiance. The proposed method leverages a voxelized scene representation for storing direct illumination and a cache of environment maps for integrating indirect illumination. By using a voxelized scene to gather indirect lighting contributions and caching these contributions spatially, we are able to achieve fast and convincing renders of large complex scenes. The result of our implementation produces images comparable to those of existing Monte Carlo integration methods with render speeds a magnitude or more faster.

Background. Rendering planets with high detail from orbit to surface level is becoming increasingly common in video games. In this thesis, two solutions to achieving this will be compared, a quadtree solution and a tessellation solution. These solutions both implement an adaptive level of detail on a spherical shape. The quadtree solution uses six quadtrees to construct the planetary terrain mesh on the CPU with higher detail closer to the viewer. The tessellation solution uses the GPU to subdivide areas of a basic low-resolution model to achieve higher levels of detail close to the viewer. Objectives. Related work that has implemented these solutions uses old hardware and there is a lack of performance data on these solutions running on modern hardware. The objective of this project is to provide performance data and a comparison between the quadtree solution and the tessellation solution on modern hardware. This comparison will include a discussion of the negative and positive performance aspects of the two solutions. Methods. The two solutions will be implemented to create two similar-looking applications with a focus on only the technical aspects of rendering a globe mesh with each of these solutions. The frame time both on the CPU and on the GPU will be measured for each solution. The measurements will be taken at four different distances from the globe, meaning four different levels of detail. Due to a limitation of tessellation, this solution has to be provided with a higher resolution base model to achieve similar detail levels at the surface level. Results. The results show the quadtree frame time increasing with measurements taken closer to the surface of the globe. The tessellation results show a larger performance impact, though this is due to the base globe mesh being swapped for a higher-resolution model. Conclusions. The result suggests that the tessellation solution performs worse, however, the tessellation solution still shows little to no performance loss when comparing frame time measured on the same base mesh, even though the detail difference between them is high. The quadtree solution has an overall better performance and provides more control over the detail levels. The lack of control over the detail levels in the tessellation solution means that the detail level can not be matched exactly, which leads to the tessellation solution giving a richer topology.

No / Advances in computer technology and developments such as the Internet provide a constant momentum to design new techniques and algorithms to support computer graphics. Modelling, animation and rendering remain principal topics in the filed of computer graphics and continue to attract researchers around the world." This volume contains the papers presented at Computer Graphics International 2002, in July, at the University of Bradford, UK. These papers represent original research in computer graphics from around the world

In recent years there has been growing interest in limitless realism in computer graphics applications. Among those, my foremost concentration falls into the complex physical simulations and modeling with diverse applications for the gaming industry. Different simulations have been virtually successful by replicating the details of physical process. As a result, some were strong enough to lure the user into believable virtual worlds that could destroy any sense of attendance. In this research, I focus on fire simulations and its deformation process towards various virtual objects. In most game engines model loading takes place at the beginning of the game or when the game is transitioning between levels. Game models are stored in large data structures. Since changing or adjusting a large data structure while the game is proceeding may adversely affect the performance of the game. Therefore, developers may choose to avoid procedural simulations to save resources and avoid interruptions on performance. I introduce a process to implement a real-time model deformation while maintaining performance. It is a challenging task to achieve high quality simulation while utilizing minimum resources to represent multiple events in timely manner. Especially in video games, this overwhelming criterion would be robust enough to sustain the engaging player's willing suspension of disbelief. I have implemented and tested my method on a relatively modest GPU using CUDA. My experiments conclude this method gives a believable visual effect while using small fraction of CPU and GPU resources.

In appreciation of High-Performance Computing, modern scientific simulations are scaling into millions and even billions of grid points. As we enter the exa-scale, new strategies are required for visualization and analysis. While Image-Based Rendering (IBR) has emerged as a viable solution to the asymmetry between data size and its storage and required rendering power, it is limited in its 2D image portrayal of 3D spatial objects. This work describes a novel technique to capture, represent, and render depth information in the context of 3D IBR. We tested the value of displacement by displacement map, shading by normal, and image angle interval with our technique. We ran an online user study of 60 participants to evaluate the value of adding depth information back to Image-Based Rendering and found significant benefits. / Master of Science / In scientific research, data visualization is important for better understanding data. Modern experiments and simulations are expanding rapidly in scale, and there will come a day when rendering the entire 3D geometry becomes impossible resource-wise. Cinema was proposed as an image-Based solution to this problem, where the model was represented by an interpolated series of images. However, using flat images cannot fully express the 3D characteristics of a data. Therefore, in this work, we try to improve the depth portrayal of the images by protruding the pixels and applying shading. We show the results of a user study conducted with 60 participants on the effect of pixel protrusion, shading, and varying the number of images representing the object. Results show that this method would be useful for 3D scientific visualizations. The resulting object almost accurately resembles the 3D object.

The sweep paradigm for volume rendering has previously been successfully applied with irregular grids. This thesis describes a parallel volume rendering algorithm called PARZSweep for regular grids that utilizes the sweep paradigm. The sweep paradigm is a concept where a plane sweeps the data volume parallel to the viewing direction. As the sweeping proceeds in the increasing order of z, the faces incident on the vertices are projected onto the viewing volume to constitute to the image. The sweeping ensures that all faces are projected in the correct order and the image thus obtained is very accurate in its details. PARZSweep is an extension of a serial algorithm for regular grids called RZSweep. The hypothesis of this research is that a parallel version of RZSweep can be designed and implemented which will utilize multiple processors to reduce rendering times. PARZSweep follows an approach called image-based task scheduling or tiling. This approach divides the image space into tiles and allocates each tile to a processor for individual rendering. The sub images are composite to form a complete final image. PARZSweep uses a shared memory architecture in order to take advantage of inherent cache coherency for faster communication between processor. Experiments were conducted comparing RZSweep and PARZSweep with respect to prerendering times, rendering times and image quality. RZSweep and PARZSweep have approximately the same prerendering costs, produce exactly the same images and PARZSweep substantially reduced rendering times. PARZSweep was evaluated for scalability with respect to the number of tiles and number of processors. Scalability results were disappointing due to uneven data distribution.

This work presents a solution for a real-time fire suppression control system. It also serves as a support tool that allows creation of virtual ship models and testing them against a range of representative fire scenarios. Model testing includes generating predictions faster than real time, using the simulation network model developed by Hughes Associates, Inc., their visualization, as well as interactive modification of the model settings through the user interface. In the example, the ship geometry represents ex-USS Shadwell, test area 688, imitating a submarine. Applying the designed visualization techniques to the example model revealed the ability of the system to process, store and render data much faster than the real time (in average, 40 times faster).

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